1. Field of the Invention
The present invention relates to a copier, multifunction peripheral, fax machine, printer, or other image-forming apparatus that includes a decurling device for removing curling from paper.
2. Description of Related Art
In some copiers, multifunction peripherals, fax machines, printers, and other image-forming apparatuses, a formed toner image is transferred to paper, and the toner image is heated and pressed by a roller, or the like, whereby it is affixed to the paper. When the toner image is fixed to the paper, the paper may curl due to contraction of the toner, evaporation of moisture in the paper, winding of the paper onto the roller due to tackiness of the toner, or other reasons. When paper is discharged in a curled state to the discharge tray, gaps between printed pages become larger, and the stacking capacity of the discharge tray is reduced. A disorderly stacking state due to catching of curled sections on discharged pages also may occur. A decurling device for removing curling from paper may therefore be provided.
For example, there is known a curl-removing device for removing curling from a recording medium in an image-forming apparatus, the curl-removing device having a roller pair including a soft roller made of a flexible material and a hard roller pressed against the soft roller in parallel with the soft roller; a casing having a recording medium conveyance path formed therein, and accommodating the roller pair so as to face the conveyance path, a roller drive device for driving the roller pair to rotate, and a casing rotation device for causing the casing to rotate around a shaft parallel with a roller shaft of the roller pair. This configuration provides a curl-removing device that takes little space compared with a conventional device, and is less likely to result in paper jams.
For example, a decurling device has a roller pair comprising a hard metal roller and a soft roller pressed against the hard roller, and toner-fixed paper is passed through a nip between the rollers to remove the curling. The decurling device is fixed in position, and the curl removal direction is therefore fixed. However, there are cases when one wishes to change the curl removal direction. Therefore, a plurality of conveyance paths is provided, and the direction for passing paper to the decurling device is changed, or two decurling devices with switched positions of the hard roller and the soft roller are provided. The aforementioned invention provides a major advantage in that the curl removal direction can be changed by the casing rotation device, and a plurality of conveyance paths or decurling devices is not necessary.
However, according to the conventional art, the user must select and set the curl removal direction, and there is a problem in convenience for the user. In the case of double-sided printing in particular, the user must predict the curl removal direction, and setting of the curl removal direction is troublesome. Also in the case of double-sided printing, the user may not be able to predict the direction in which the paper curls. The paper may therefore end up passing through the decurling unit in a direction whereby curling is exacerbated. Consequently, there is also a problem that decurling may not be accomplished assuredly.